1. Field of the Invention
This invention relates to a railroad switch stand of simple yet highly effective construction which has numerous advantages including ease of operation by a switchman without bending over, automatic locking, and automatic disconnecting in the event a train runs through the switch that is lined against it, for example. More particularly, it is concerned with a switch stand having a hand operable, rotatable throw wheel mounted at about normal chest height, means coupling the throw wheel with the throw rod for translating rotation of the throw wheel into longitudinal movement of the rod, a locking bar for engaging a slot in the wheel, and a shear pin breakable for disconnecting the throw rod if excessive axial force is applied thereto.
2. Description of the Prior Art
U.S. Pat. No. 401,671 issued to Alkins in 1889, illustrates one type of railway switch stand still in common usage today. This type of switch stand is operated by lifting and rotating a weighted rod from one position to another. This type of switch stand has the substantial disadvantage of subjecting the switchman to potential back and leg injury.
Another type of switch stand in common usage is known as the HIGHSTAR manufactured by Pettibone-Mulliken. This switch stand includes a vertical throw shaft with a link affixed to the lower end and extending outwardly on opposed sides thereof. Each end of the link includes an upwardly extending boss selectively and pivotally received in a pivot hole defined in the outboard end of the switch throw rod. A pair of retaining brackets retain the throw rod engaged with the selected boss. The throw shaft also includes a vertically pivotal, lockable, outwardly extendable handle used as a lever to rotate the throw shaft. The upper end of the throw shaft includes a banner or target for indicating the position of the switch.
Attempts to improve on the commonly used switch stand designs have not come into widespread usage perhaps because of mechanical complexity and the associated installation and maintenance cost. For example, U.S. Pat. No. 3,652,849 illustrates a foot-operated, switch-connected lever movable to operate a switch between open and thrown positions. This type of switch stand, however, presents greater mechanical complexity than desired and may become inoperable if snow or gravel become piled under the foot pedals of the device.
Some prior art devices, such as that illustrated in U.S. Pat. No. 1,325,396, employ a rotatable wheel mounted at track level. This requires a switchman to bend over to operate the wheel subjecting the switchman to potential back injury. Additionally, this type of switch does not provide a mechanism for automatically locking the switch stand in the open or thrown to indicate that the switch is not positioned therebetween.
Finally, prior art switch stands are susceptible to damage when a train runs through a switch that is lined against it. When this happens, the movable rails of the switch force the throw rod to move axially which can severely damage the mechanism of the switch stand and the switch itself. Conversely, if the rails of the switch become immovable due to snow, ice, gravel, or the like, forcible operation of the switch stand also causes excessive axial force on the throw rod which can similarly damage the mechanism of the switch stand. None of the known prior art devices provides a means for automatically disconnecting the mechanism in the switch stand from the throw rod whenever excessive axial force is applied thereto in order to prevent damage to the switch stand mechanism and the throw rod.